For high track density recording, tighter reader and writer track width control is the key ingredient for obtaining high yield. How to continue improving the writer track width by using a pole trim process together with a narrow pole width is a challenging task. The basic principle to having tighter pole width control is to have a thinner pole resist process so that photo CD (critical dimension) control can be further improved. Reducing the amount of material consumed during the pole trim process, without impacting performance, is the key factor associated with using a thinner pole resist.
The magnetic track width delta between reader and writer must be significantly reduced in high track density recording. Therefore, it becomes necessary to have better within-wafer reader and writer uniformity in order to meet performance requirements and provide a better yield. However, a pole trim process is required if one is to have a well defined track profile that facilitates the writing operation.
On the other hand, said pole trim process introduces new problems such as track width uniformity control which needs to be improved. To achieve this, one must either remove less material during trimming or an improved trimming method must be substituted. The present invention discloses a novel process that allows less material to be removed during trimming while continuing to maintain the same performance level as the standard pole trim process
There have been several proposals to utilize a plated S2 (writer lower shield), a plated write gap, and a plated P2 (top pole) in a single photo process thereby minimizing the extent of pole trim consumption. However, with this scheme the throat height definition is rather poor so this type of design creates magnetic flux leakage between pole and shield. So poor overwrite is a consequence of this type of design.
Referring now to FIG. 1, the structure associated with our earlier process is illustrated. Seen there are upper and lower magnetic shields 13 and 15 respectively. Sandwiched between these shields is reader assembly 14. High magnetic moment seed layer 21 lies atop layer 13 with non-magnetic write gap layer 51 being on it. Covering layer 51 is P2 seed layer 31 on which P2 pole 52 is formed through electroplating inside a mold (not shown).
In FIG. 2 we illustrate the end product of the pole trimming process during which part of P2 is etched away together with the exposed portions of layers 21, 51, and 31. During this trim process, portions of the wafer surface away from the immediate vicinity of P2, such as test sites, will need to protected. Since the resist gets consumed at least as rapidly as the pole material, its thickness must exceed the amount of P2 removed during trimming. Resist thicknesses of 2-3 microns must therefore be used.
A routine search of the prior art was performed with the following references of interest being found:
U.S. Pat. No. 6,469,868 (Yanamoto et al) teaches that a seed layer may be made of a nonmagnetic and a conductive material. U.S. Pat. No. 6,636,460 (Akiyama et al) discloses a Ni or NiFe sputtering film as a plating seed layer. U.S. Pat. No. 5,559,654 (Das) teaches plating on a previously sputtered seed layer.